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Added syntax properties to mark @-form datum and body number of subexprs

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svn: r6902

original commit: 108b23e491e7965939f6b80e0b13b19363afc499
This commit is contained in:
Eli Barzilay 2007-07-13 04:45:14 +00:00
parent b5928162f5
commit 6f39353a52
2 changed files with 115 additions and 43 deletions
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77
collects/scribble/doc.txt
View File

@ -570,34 +570,65 @@ matter, you can begin (or end) a line with a "@||".
@|| bar @|| --reads-as--> (foo " bar " "\n" " baz")
@|| baz}
Finally, you might be need a verbatim-like environment, where the
parsed body matches exactly the textual source. To make this
possible, the @-parser uses syntax properties on the resulting syntax
values. All items that are not physically in the Scribble source --
newlines and indentation-spaces -- have a 'scribble property. An
indentation string will have 'indentation as the value of this
property, and a newline will have a '(newline S) value where S is the
original newline string including spaces that precede and follow it
(which includes the indentation for the following item). To implement
a verbatim environment you need to drop indentation strings, and use
the original newline strings instead of the single-newline string.
* Syntax Properties
The Scribble reader attaches properties to syntax objects. These
properties might be useful in rare situations.
Forms that Scribble reads is marked with a 'scribble property, and a
value of a list of three elements: the first is 'form, the second is
the number of items that were read from the datum part, and the third
is the number of items in the body part (strings, sub-forms, and
escapes). In both cases, a 0 means an empty datum/body part, and #f
means that the corresponding part was omitted. If the form has
neither parts, the property is not attached to the result. This
property can be used to give different meanings to expressions from
the datum and the body parts, for example, implicitly quoted keywords:
(define-syntax (foo stx)
(let ([p (syntax-property stx 'scribble)])
(syntax-case stx ()
[(_ x ...)
(and (pair? p) (eq? (car p) 'form) (even? (cadr p)))
(let loop ([n (/ (cadr p) 2)]
[as '()]
[xs (syntax->list #'(x ...))])
(if (zero? n)
#`(list 'foo `#,(reverse as) #,@xs)
(loop (sub1 n)
(cons #`(#,(car xs) ,#,(cadr xs)) as)
(cddr xs))))])))
@foo[x 1 y (* 2 3)]{blah}
--> (foo ((x 1) (y 6)) "blah")
In addition, the Scribble parser uses syntax properties to mark syntax
items that are not physically in the original source -- indentation
spaces and newlines. Both of these will have a 'scribble property; an
indentation string of spaces will have 'indentation as the value of
the property, and a newline will have a '(newline S) value where S is
the original newline string including spaces that precede and follow
it (which includes the indentation for the following item). This can
be used to implement a verbatim environment: drop indentation strings,
and use the original source strings instead of single-newline string.
Here is an example of this.
(define-syntax (verb stx)
(syntax-case stx ()
[(_ cmd item ...)
#`(cmd .
#,(let loop ([items (syntax->list #'(item ...))])
(if (null? items)
'()
(let* ([fst (car items)]
[prop (syntax-property fst 'scribble)]
[rst (loop (cdr items))])
(cond [(not prop) (cons fst rst)]
[(eq? prop 'indentation) rst]
[else (cons (datum->syntax-object
fst (cadr prop) fst)
rst)])))))]))
#`(cmd
#,@(let loop ([items (syntax->list #'(item ...))])
(if (null? items)
'()
(let* ([fst (car items)]
[prop (syntax-property fst 'scribble)]
[rst (loop (cdr items))])
(cond [(eq? prop 'indentation) rst]
[(not (and (pair? prop)
(eq? (car prop) 'newline)))
(cons fst rst)]
[else (cons (datum->syntax-object
fst (cadr prop) fst)
rst)])))))]))
@verb[string-append]{
foo
bar

81
collects/scribblings/scribble/reader.scrbl
View File

@ -631,18 +631,59 @@ matter, you can begin (or end) a line with a "@||".
@|| baz}
}===|
Finally, you might be need a verbatim-like environment, where the
parsed body matches exactly the textual source. To make this
possible, the @"@"-parser uses syntax properties on the resulting
syntax values. All items that are not physically in the Scribble
source---newlines and indentation-spaces---have a 'scribble property.
An indentation string will have @scheme['indentation] as the value of
this property, and a newline will have a @scheme['(newline S)] value
where S is the original newline string including spaces that precede
and follow it (which includes the indentation for the following item).
To implement a verbatim environment you need to drop indentation
strings, and use the original newline strings instead of the
single-newline string. Here is an example of this.
@subsubsub*section{Syntax Properties}
The Scribble reader attaches properties to syntax objects. These
properties might be useful in rare situations.
Forms that Scribble reads is marked with a @scheme['scribble]
property, and a value of a list of three elements: the first is
@scheme['form], the second is the number of items that were read from
the datum part, and the third is the number of items in the body part
(strings, sub-forms, and escapes). In both cases, a @scheme[0] means
an empty datum/body part, and @scheme[#f] means that the corresponding
part was omitted. If the form has neither parts, the property is not
attached to the result. This property can be used to give different
meanings to expressions from the datum and the body parts, for
example, implicitly quoted keywords:
@; FIXME: a bit of code duplication here
@def+int[
(define-syntax (foo stx)
(let ([p (syntax-property stx 'scribble)])
(syntax-case stx ()
[(_ x ...)
(and (pair? p) (eq? (car p) 'form) (even? (cadr p)))
(let loop ([n (/ (cadr p) 2)]
[as '()]
[xs (syntax->list #'(x ...))])
(if (zero? n)
(with-syntax ([attrs (reverse as)]
[(x ...) xs])
#'(list 'foo `attrs x ...))
(loop (sub1 n)
(cons (with-syntax ([key (car xs)]
[val (cadr xs)])
#'(key ,val))
as)
(cddr xs))))])))
(eval:alts
(code:line
#, @tt["@foo[x 1 y (* 2 3)]{blah}"])
@foo[x 1 y (* 2 3)]{blah})
]
In addition, the Scribble parser uses syntax properties to mark syntax
items that are not physically in the original source --- indentation
spaces and newlines. Both of these will have a @scheme['scribble]
property; an indentation string of spaces will have
@scheme['indentation] as the value of the property, and a newline will
have a @scheme['(newline S)] value where @scheme[S] is the original
newline string including spaces that precede and follow it (which
includes the indentation for the following item). This can be used to
implement a verbatim environment: drop indentation strings, and use
the original source strings instead of single-newline string. Here is
an example of this.
@; FIXME: a bit of code duplication here
@def+int[
@ -656,21 +697,21 @@ single-newline string. Here is an example of this.
(let* ([fst (car items)]
[prop (syntax-property fst 'scribble)]
[rst (loop (cdr items))])
(cond [(not prop) (cons fst rst)]
[(eq? prop 'indentation) rst]
(cond [(eq? prop 'indentation) rst]
[(not (and (pair? prop)
(eq? (car prop) 'newline)))
(cons fst rst)]
[else (cons (datum->syntax-object
fst (cadr prop) fst)
rst)])))))]))
(eval:alts
(code:line
#, @tt["@verb[string-append]{"]
#, @tt[" foo"]
#, @tt[" bar"]
#, @tt["}"])
@verb[string-append]{
foo
bar
})
@verb[string-append]{
foo
bar
})
]